This directive never was documented, and it should not be used
unless you understand what this directive does and associated
risks. It is not officially supported.
--
Maxim Dounin
nginx.org
calculate: function( value ){
var hours = Math.floor( value / 60 );
var mins = ( value - hours*60 );
return (hours < 10 ? "0"+hours : hours) + ":" + ( mins == 0 ? "00" : mins );
}, false.
nginx.conf